We want to understand the regulation of the growth rate in bacteria. This problem requires that we find the mechanisms by which the synthesis and function of ribosomes and RNA polymerase are controlled. We are using the physiologically well-characterized bacterium E. coli B/r for genetic and physiological studies and purified E. coli RNA polymerase and DNA for in vitro studies. Genetically we are searching for ribosome control genes; physiologically, we are analysing ribosome and RNA polymerase synthesis in response to the inhibition of growth rate-limiting reactions. In vitro, we want to measure the chain growth and initiation rates of ribosomal RNA and mRNA for ribosomal proteins, as a function of ionic conditions. It is our aim to integrate our findings into a theory of cell growth.